create table users(
    id integer primary key,
    firstname varchar(255),
    lastname varchar(255),
    login varchar(255)
);

create table meetings(
    id integer primary key,
    description text,
    meeting_datetime datetime,
    participants text,
    leader_id integer,
    meeting_link varchar(255),
    chat_id integer,
    FOREIGN KEY(leader_id) REFERENCES users(id)
);

create table notifications(
    id integer primary key,
    when_notify varchar(255),
    meeting_id integer,
    chat_id integer,
    message text,
    FOREIGN KEY(meeting_id) REFERENCES meetings(id)

);

